1. Field of the Invention
The present invention relates town optical axis adjusting screw which can prevent a generation of foreign matters due to a sliding motion during an optical axis adjusting operation for adjusting an irradiating direction of a lamp unit in a vehicle headlamp.
2. Related Art
In vehicle headlamps, there is, for example, a type in which a lamp unit having a light source is disposed in an interior space of a lamp outer casing which is made up of a cover and a lamp body.
In vehicle headlamps of this type, there is a vehicle headlamp in which an aiming adjustment which is an initial adjustment of a light irradiating direction is enabled by an optical axis adjusting mechanism (refer to JP-A-2002-193023, for example).
In the vehicle headlamp described in JP-A-2002-193023, an optical axis adjusting mechanism supports a lamp unit at three support points which are spaced apart vertically and horizontally so that the lamp unit is tilted freely relative to a lamp body. Optical axis adjusting screws are provided on the optical axis adjusting mechanism, and these optical axis adjusting screws function as two of the three support points.
The optical axis adjusting screws are formed by integrally molding, through injection molding which employs a mold, a shaft portion having a shaft-like shape and extending in a front-rear direction, a gear portion which is connected to a rear end of the shaft portion, and a pair of elastic engagement portions which project outwards from a position on the shaft portion which lies closer to a rear end.
The shaft portion includes a threaded portion which is brought into meshing engagement with a screw support portion which is provided in the lamp unit and a support shaft portion which is supported rotatably on the lamp body.
The elastic engagement portions is inserted into a support hole formed in the lamp body from a rear side, and the optical axis adjusting screws are rotatably supported on the lamp body by the shaft portion. In order to insert the elastic engagement portions into the support hole in the lamp body, the pair of elastic engagement portions are elastically deformed in a direction in which the elastic engagement portions approach each other. The elastic engagement portions are elastically restored to their initial positions when they are entirely inserted through the support hole, whereby respective rear surfaces of the elastic engagement portions are brought into contact with an inner surface of the lamp body. Consequently, the optical axis adjusting screws are prevented from being dislodged to the rear side relative to the lamp body by the elastic engagement portions being brought into contact with the inner surface of the lamp body.
In the vehicle headlamp configured in the way described above, when the gear portion of the optical axis adjusting screw is operated to rotate, the screw support portion is fed in a direction corresponding to the rotating direction of the gear portion, whereby the lamp unit is tilted relative to the lamp body on the other two support points as fulcrums. Thus, an optical axis adjustment (an aiming adjustment) is effected so as to adjust the irradiating direction of light.
As has been described above, the optical axis adjusting screw is formed integrally by the injection molding which employs the mold, and the mold is formed by a pair of dies which are opened and closed in a direction which is at right angles to an axial direction of the shaft portion.
Consequently, parting lines extending in the axial direction of the shaft portion are formed on the optical axis adjusting screw, and a parting line is formed also on the rear surfaces of the pair of elastic engagement portions at centers in a left-right direction.
In the event that the parting line is formed on the rear surfaces of the elastic engagement portions, when the optical axis adjusting screw is rotated relative to the lamp body during an adjusting operation of the optical axis, the parting line on the rear surface of the elastic engagement portion would caused to slide against an inner surface of the lamp body, whereby foreign matters such as abrasion dust may be generated or the inner surface of the lamp body may be abraded.